Physical Results from Unphysical Simulations

TL;DR

This paper uses chiral perturbation theory to analyze properties of pseudoscalar mesons in partially quenched QCD, enabling the extraction of physical parameters from unphysical simulations with three light dynamical quarks.

Contribution

It provides a method to extrapolate physical quantities from partially quenched simulations and introduces a novel approach to determine L_7 using unphysical effects.

Findings

Calculated meson properties using next-to-leading order chiral perturbation theory.

Proposed a new method to determine L_7 from unphysical effects.

Results applicable to simulations with up to three different sea quark masses.

Abstract

We calculate various properties of pseudoscalar mesons in partially quenched QCD using chiral perturbation theory through next-to-leading order. Our results can be used to extrapolate to QCD from partially quenched simulations, as long as the latter use three light dynamical quarks. In other words, one can use unphysical simulations to extract physical quantities - in this case the quark masses, meson decay constants, and the Gasser-Leutwyler parameters L_4-L_8. Our proposal for determining L_7 makes explicit use of an unphysical (yet measurable) effect of partially quenched theories, namely the double-pole that appears in certain two-point correlation functions. Most of our calculations are done for sea quarks having up to three different masses, except for our result for L_7, which is derived for degenerate sea quarks.